Disk drives, also called disk files, are information storage devices that use a rotatable disk with concentric data tracks containing the information, a head or transducer for reading and/or writing data onto the various tracks, and an actuator connected to a carrier for the head for moving the head to the desired track and maintaining it over the track centerline during read or write operations. There are typically a plurality of disks separated by spacer rings and stacked on a hub that is rotated by a disk drive motor. A housing supports the drive motor and head actuator and surrounds the head and disk to provide a substantially sealed environment for the head-disk interface.
In conventional magnetic recording disk drives, the head carrier is an air-bearing slider that rides on a bearing of air above the disk surface when the disk is rotating at its operational speed. The slider is maintained next to the disk surface by a relatively fragile suspension that connects the slider to the actuator. The slider is either biased toward the disk surface by a small spring force from the suspension, or is "self-loaded" to the disk surface by means of a "negative-pressure" air-bearing surface on the slider.
To improve the wear resistance of the disk, as well as to maintain consistent magnetic properties, it is desirable to make the disk surface as smooth as possible. However, a very smooth disk surface creates a problem known as "stiction". This means that after the slider has been in stationary contact with the disk for a period of time, the slider tends to resist translational movement or "stick" to the disk surface. Stiction is caused by a variety of factors, including static friction and adhesion forces between the disk and slider created by the lubricant on the disk. Stiction in a disk drive can result in damage to the head or disk when the slider suddenly breaks free from the disk surface when disk rotation is initiated. In addition, because the suspension between the actuator and the slider is relatively fragile in order to permit the slider to fly above the disk surface, sudden rotation of the disk can also damage the suspension. In some disk drives, such as low-power disk drives used in laptop and notebook computers, the drive motor may simply be unable to initiate rotation or achieve operating speed because of the adhesion forces that cause stuck sliders or excessive drag.
Contact start/stop (CSS) disk drives operate with the slider in contact with the disk surface during start and stop operations when there is insufficient disk rotational speed to maintain the air bearing. To minimize the effect of stiction, CSS disk drives often use a dedicated textured "landing zone" where the slider is parked when the drive is not operating. Typically, the landing zone is a specially textured nondata region of the disk. The disk substrate is textured before deposition of the magnetic layer and other layers that make up the magnetic recording disk. These layers replicate the texture of the underlying substrate and thus reduce the stiction when the slider is resting on the disk.
One technique for texturing the disk substrate is by pulsed laser radiation. U.S. Pat. No. 5,108,781, assigned to Magnetic Peripherals, Inc., describes a process for laser texturing by forming overlapping pits or craters in the substrate. IBM's copending application, Ser. No. 08/150,525, describes a process for using a diode-pumped laser for texturing the disk substrate with an array of spaced-apart bumps. IBM's copending application, Ser. No. 08/149,851, describes a process for laser texturing glass disk substrates. The problem discovered with laser textured disk substrates is that the average height of the laser-induced bumps can not be controlled from substrate to substrate, even when the substrates are presumably of the same material composition. Since the minimization of stiction is critically dependent on the average height of the texturing bumps, it is necessary to develop a process that allows a texturing pattern with a known average bump height to be formed on all disks that are manufactured, thus assuring reliable operation of the disk drives into which the disks are incorporated.